Australia’s Retail Employees Superannuation Trust (REST) is joining the bid group led by Australasian investment manager Morrison & Co that also features Wellington-based infrastructure investor Infratil and the New Zealand Superannuation Fund.

The consortium has emerged as the key rival to Manchester Airports Group (MAG) after the first round of the £1bn bid battle for the Essex airport. Two financial bidders, Macquarie and TPG, also submitted first round bids, though neither are yet thought to have the necessary financing in place.

Since then, Stansted’s owner Heathrow – the company formerly known as BAA – has sought to liven up the auction by attracting some interest from Malaysia Airports Holdings, the owner of 39 airports in its home market including Kuala Lumpur International.

REST, which has 1.9m members and is one of Australia’s biggest retirement funds, has already made one unsuccessful attempt to buy a UK airport. Earlier this year it bid alongside JP Morgan for Edinburgh, the airport BAA sold for £807m to Global Infrastructure Partners, the owner of Gatwick and London City airports.

Morrison & Co was keen to add another investor to its consortium because financing Stansted is expected to require a hefty equity cheque. Sources close to the auction believe bidders may have to put in about £400m of equity, with the rest funded by debt.

The relative youth of many of REST’s members allows it can invest for the long-term, with less pressure to make a quick turn on any assets it owns.

REST, which has £15bn under management, already has some involvement in the UK market via a small holding in Southern Water.

The Australian pension fund also knows Ferrovial, the Spanish construction group that led 2006’s £10.3bn purchase of what was then known as BAA. Last month REST teamed up with Ferrovial subsidiary Cintra to invest in and operate toll-road projects in Australia.

MAG is also being backed by an Australian investor, Industry Funds Management, which has £21bn under management.